The achilles tendon, showing a thickened area typical of achilles tendonitis

Achilles tendonitis is often now being referred to as achilles tendinopathy. This is because it is no longer thought to be an inflammatory condition. On investigation, the main finding is usually degenerated tissue with a loss of normal fibre structure.

Achilles tendonitis can be either acute, meaning occurring over a period of a few days, following an increase in training, or chronic which occurs over a longer period of time. In addition to being either chronic or acute, the condition can also be either at the attachment point to the heel or in the mid-portion of the tendon (typically around 4cm above the heel). Healing of the achilles tendon is often slow, due to its poor blood supply.

 (From...Sports Injury clinic www.sportsinjuryclinic.net)